The very last thing in the world I would have wanted as a girl was having men talk about my womb and vagina. It was humiliating enough having boys talk about periods because, hey, it was interesting to them that they could talk about girls' bodies instead of girls as sentient humans, it involved vaginas (hurr, hurr, hurr), putting things inside vaginas (as per the bag snatches where they'd search and a box of tampons was the top prize, dancing around with them, shouting 'You're not a virgin!' and other vile stuff) and, most important of all, it kept the girls in their place with boys taking control through humiliation and mockery. All giving boys information about menstruation did was give them more words to target girls with.
Then, as you got older, you'd have men treating you as unclean because you were menstruating, accusing you of being on the blob if you weren't happy about how they were treating you, mocking you for feeling like crap or telling you that it can't be that bad, really, repeating misogynistic stuff like 'never trust an animal that can bleed for week a month and not die' and then there's the practicalities, of finding toilet facilities that haven't been colonised by males for various reasons, of dysfunctional menstruation being dismissed by doctors, and so on.
And it's now something a bloke gets paid a fuckton to lecture us about menstruation because he's the best person to talk about women, girls and their bodies? Piss off.